1. Field of the Invention
The present invention relates to a program transmission system used for, for example, a CATV (Community Antenna Television or Cable Television) system and the like, and more particularly relates to a system for transmitting a program, in accordance with a request from a viewer.
2. Description of the Related Art
A CATV has been known as a system for mainly transmitting a TV signal through a cable. A center device in this CATV broadcasts a sustaining program, a re-transmission (not equal to a so-called re-broadcast) of a broadcast program received from another broadcasting station, or a program already stored in a memory medium (a movie and the like). Those programs are broadcast in accordance with a broadcast schedule. The re-transmission implies that a program received from another broadcasting station is broadcast in its original state although a channel conversion may be carried out. On the other hand, the re-broadcast implies that a part of the program (mainly, a popular program) broadcast in accordance with the broadcast schedule is again added into the broadcast schedule and broadcast.
The broadcast schedule in the CATV specifies a broadcast channel of each program, a broadcast start time, a length of a program or a broadcast end time and the like, similarly to that of a typical television station or the like.
A viewer can know a desirable program by using a television program table announcing the schedule on a newspaper, a magazine and the like, or a recently popularized EPG (Electronic Program Guide).
A program currently being broadcast or a future program can be selected by using this EPG. In a case of the program currently being broadcast, it is possible to immediately receive the broadcast channel. In a case of the future program, it is possible to store a broadcast channel of the program, a broadcast start time, a length of the program or a broadcast end time, and the like. The broadcast channel of the program is received at the broadcast time of the program. The program received at this time can be automatically stored by controlling a connected VTR.
The CATV broadcast has been digitized so that it becomes easier to make a data reception such as a schedule information and the like, or transmit a terminal information to a center device.
On the other hand, VOD (Video On Demand) or NVOD (Near Video On Demand) has been known as a service type to give a program to a viewer. In brief, after a reception of a request from the viewer, a program is broadcast to the viewer at least requesting the program in the VOD. In a case of the NVOD, irrespective of a presence or absence of the request from the viewer, the same program is repeatedly broadcast to an indefinite number of viewers in a normal case, through a plurality of channels, while the broadcast time is shifted. In short, in the case of the NVOD, the program is transmitted in accordance with a schedule. It is possible to select a suitable channel in the EPG. This is used, for example, in a picture library in which a visitor to a library, a museum or the like can request a desirable picture from a terminal to thereby view the picture stored in a database in advance.
However, in the conventional program view system, the already broadcast program is not displayed in the EPG. Even if it is displayed, the viewer can not select it. That is, there is no system in which the viewer can view a past program broadcast in accordance with a schedule. Thus, if the viewer forgets to set (reserve) a recording of program desired by the viewer, or if the viewer is aware of the program desired by the viewer after the program is broadcast, the viewer can not view the program.